Polymerization of styrenes in the presence of alcohol diluents and unsaturated peroxides



Patented Feb. 27, 1951 POLYDIEBIZATION OF STYRENES IN THE PRESENCE OF ALCOHOL DILUENTS AND UNSATURATED PEBOXIDES Hanns Peter Staudinger, Ewell, England, assignor to The Distillers Company Limited, Edinburgh, Scotland, at British company No Drawing. Application August 24, 1944, Serial No. 551,067. In Great Britain July 21, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires July 21, 1963 6 Claims. 1

This invention relates to the preparation of synthetic resins by the polymerisation oi styrene, alpha-methyl styrene or nuclear-alkyl-substituted styrenes or mixtures of these substances.

The methods usually employed for polymerising styrene to resins of high molecular weight consist either of heating the monomeric substance, in the presence or absence of polymerisation catalysts, either by itself, or in the presence of a solvent-diluent (by which is meant a solvent for both monomer and polymer) or a nonsolvent-diluent (by which is meant a substance which is a solvent for the monomer and a nonsolvent for the polymer), or in the form of an aqueous emulsion. It is known that various factors, amongst which are the temperature of polymerisation, the concentration of the monomer in the diluent, the catalyst concentration and the proportion of those substances, if present, which inhibit or retard polymerisation. influence the molecular weight of the resulting polymer. In most cases, articularly in the polymerisation of the pure monomer, the molecular weight remains fairly constant throughout polvmerisation. n the other hand, if polymerisation is carried out in a solvent-diluent, which, as above defined, is a solvent for the monomer as Well as for the polymer, the molecular weight of the polymer obtained (as determined by v sco ity measurements) decreases with progressive polymerisation.

I have now found that I can prepare polvmers of styrene or stvrene derivatives, as defined above, which show. with progressive polymerisation. an increase of viscosity and which becomes decreasingly soluble and may even become in oluble in contrast to polymers prepared in the absence of cross-linking agents (as defined by H. Staudinger and W. Heuer in Berichte der Deufschen Chemischen Gesellschaft, volume 67 (1934) pages 1164 et seq.) which are soluble in benzene, carbon tetrachloride and toluene.

According to the present invention, a process for the production of a synthetic resin comprises polymerising styrene, alpha-methyl-styrene or a nuclear-alkyl-substitution product thereof separately or in any combination by the action of heat in the presence of a peroxidic catalyst containing the radicle of an unsaturated organic acid as hereinafter defined, and in the presence of a non-solvent-diluent, as hereinbefore defined, at a temperature not in excess of 150 C. The unsaturated organic acids whose radicles can be pounds which contain a pair of aliphatic double bonded carbon atoms but which have no pronounced tendency to polymerisation by themselves; examples of such compounds are crotonic acid and cinnamic acid. Compounds such as methacrylic acid, which has a pronounced tendency to polvmerlse, should not be used as there would be co-polymerisation between the acid (produced by decomposition of the peroxidie catalyst) and the styrene or alkyl-substltuted styrene; thus methacrylic peroxide is not a peroxidic catalyst which falls within the type of catalyst to be used in carrying this invention into efiect.

I find that when styrene is polymerised in the presence oi a non-solvent diluent in accordance with the process of this invention, polymers are obtained which, with progressive polymerisation, increase in viscosity until they become insoluble in solvents such as benzene, toluene and carbon tetrachloride.

I have observed that, when polymerisation is carried out with the aid 01' benzoyl peroxide as catalvst instead of a peroxidic catalyst containing the radicle 01 an unsaturated organic acid as hereinbefore defined, but under otherwise identical conditions, the viscosity of the polymers does not increase appreciably with progressive polymeri ation. Again, on the other hand, if polymerisation of styrene is carried out in presence of, for example, crotonyl peroxide. and in the presence of a diluent such as benzene, which is a solvent for both the monomer and the polymer (1. e. a solvent-diluent), no increase in the viscosity of the resultin polymers with progressive polymerisation is obtained.

From the results given below in the table. it can be seen that the viscosity increase and the insolubility oi the polymer is due to the combination of two factors, namely the presence of the selected type of peroxide catalyst and the nonsolvent diluent.

The nature of the non-solvent diluent is important. I have, for example, ascertained that methanol has the greatest precipitating action for the polymer. Other alcohols such as ethyl aloohol, amyl alcohol or (ii-acetone alcohol may also be used. To accentuate the precipitat ng action in the latter cases I prefer to add to the alcohol a small amount of water. other liquids which are inert and are non-solvent diluents, for example, acetic acid or heptane, may also be used. Thus, for example, the polymerisation present in the peroxidic catalyst are those commay be carried out in ethyl alcohol containing 3 4% by weight of water, or acetic acid containing to 6% byweight of water.

The following table shows the variation in the rate of polymerisation and the relative viscosity 4 may lead to products of less desirable properties or may lead to a rate of polymerisation which is too great for industrial application. The effect of catalyst concentration may be seen from of the su g p ers in relatio to times the following tableinwhichtheresults are given The relative viscosity expressed by the fraction for polymerisation at 80' C. of mixtures of 70% N. by volume of styrene and.30% by volume of if. methanol with 0.2% and 0.1% by weight of I crotonyl peroxide as catalyst.

in which N. is the viscosity of the solution and N0 the viscosity of the solvent, was determined ofthepolymerinbenseneat25 C.inaNo.2

U-tube viscometer B. S. S. 188 (1937) Time (hrs) 0.1 0.2

Polymerisation of a mixture of 70% b volume of styrene and 30% b volume of methanol in 531.1 v ggi" a1% iifiifl? the presence of 0.2% by weight of crotonill perocideat80'C. no 2.41 use 2.32

45.5 147 67.6 2. 68 is s: s: Timeflfl'l) mg If g a: g FnYe1'3iL-.

a a; (The solution obtained at 48 hours using 0.2% 850 by weight of catalyst appeared to contain frag- 3 g ha ments of undissolved, 11 8 11! swollen polymer.)

It is preferable to carry out polymerisations at temperatures between about 50' and 100 C. Here The amount of non-solvent diluentinthe polyagain, the po y r P p y carrying Out merisation mixture is important, as it was found polymerisation at lower temperatures show more that the rise in the viscosity of the polymers is valuable properties than the polymers prepared more pronounced in presence of higher proporat hi h temperatures. o the h r hand. tions of non-solvent diluents; to show this effect. d cr as in t mp rature nsi a y d reas d mixtures of styrene and methanol have been the rate of polym r Bflflonpolymerised at 80 C. in the presence of a 0.2% The polymerisation can be carried out with by weight of crotonyl peroxide in the following or without agitation in glass-lined vessels or in proportiom by weight: (A) 70 parts styrene to vessels of stainless steel or in vesels with tinned 30 parts methanol, (13) 60 parts styrene to Or enamelled surfaces. In many cases, where parts methanol and (C) equal parts of styrene 40 methanol is used as a diluent and the temperaand methanol and the results are tabulated ture of polymerisation is above the boiling point below: of the mixture, pressure vessels have to be used.

Time (Bra) 2 0 10 1s 24 44 00 a A a: a: .s. B 2&2 50.0 59.5 67.5 68.0 68.6 00.1

1.47 1.63 2.10 4.65 insol. msol. insoi. mm c 20.0 4&4 56.1 62.2 03.5 as t 04.1 1.15 1.42 2.05 insol. insol. lnsol. msol.

In general, a concentration of from 10% to It is also possible, as an alternative, to use a 80% by weight of non-solvent diluent in the mixreflux condenser in conjimction with the polyture undergoing polymerisation is preferred. merisation vessel when polymerising at tempera- Greater dilutions also cause a rise in the viscosity ture higher th t wn-eypondmg boning point of the resulting polymers, but the rate of reaction f the mixt r d t e c cy 0r pol m risa io is reduced The following examples illustrate the manner a d the Process beoomes 185$ economical- At the in which the invention can be carried into effect. same time, the initial molecular weight (exe0 pressed in terms of viscosity) is lower, the greater Example 1 is the dilution. In additio when us less than 10 by weight, or even t t s i weight, A mixture of 600 g. SW and 300 8- methanol of a non-solvent diluent in the mixture, the rewhich had been added 8- cmwnyl Peroxide, action is liable to cause temperature fluctuations was heated in an enamened Pressure Vessel the ma owing to the exomermic na hours at 85 C. we end of this the ture of the polymerisation reaction This is par pressure was released and the methanol blown ticularly disadvantageous when working in large of! through a condenser. When most of the batches, where heat dissipation is more difllcult methanol had e o ed, the contents o the t acmeva vessel were heated to 120 C. and vacuum was ap- I prefer to use an amount of catalyst between plied so as to remove residual diluent and un- 0.05% and 1% by weight of the total mixture; polymerised styrene. The polymer was obtained less catalyst may, however, be used at the exin a yield of 91% and found to be insoluble in pense of time of polymerisation. Higher probenzene. On extruding this material through a portions of catalyst, may be employed, but these heated die, it flowed very freely.

Example 2 A mixture of ten parts by volume of styrene,

9.5 parts by volume of ethanol and 0.5 part by,

volume of water were polymerised in the presence of .05 part by weight of crotonyl peroxide at 60 C. After 72 hours the polymer was obtained in 82% ield; it was insoluble in benzene but showed satisfactory flow properties.

Example 3 I 350 cos. of monomeric styrene (of 93.8% purity) together with 150 ccs. methanol were polymerised in the presence of 1.5 g. cinnamyl peroxide, using a cylindrical enamelled pressure vessel. This vessel was immersed in a water bath at 90 C. for 48 hours. At the end of that period, methanol was vented off and the polymer transferred on a tray into a vacuum oven, heated to 100 C. The polymer after 24 hours heating at 100 C. under 25 mm. pressure, was in the form of a cellular lump which could easily be broken up. This polymer was found to swell but not dissolve in benzene or toluene. A polymer prepared under identical conditions, but using an equivalent amount of benzoyl peroxide instead of cinnamyl peroxide, was soluble. (Relative viscosity=2.05 in a 2% benzene solution at 25 C. in B. S. S. 188 (1937) U-tube No. 2 viscometer). In addition the cinnamyl peroxide polymer gave,

' when plasticised, with 40% by weight of the plasticiser known under the registered trademark Polymeth (consisting of the mixed lower polymers of alpha-methyl styrene) a pliable composition of considerably less tackiness than the polymer obtained using benzoyl peroxide.

What I claim is:

1. A process for the production of a synthetic resin which comprises polymerising a compound of the class consisting of styrene and alphamethyl styrene by heating said compound to a temperature not in excess of 150 C. in the presence of a peroxidic catalyst containing the radicle of an unsaturated organic acid of the group consisting of crotonic and cinnamic acids, and in the presence of a diluent consisting of an aliphatic alcoho1 containing not more than five carbon atoms in the molecule.

2. A process according to claim 1 wherein said diluent is methanol.

3. A process for the production of a synthetic resin which comprises heating styrene to a temperature of from to 100 C. in the presence of methanol and in the presence of crotonyl peroxide.

4. A process for the production of a synthetic resin which comprises heating, to a temperature of from 50 to 100 C. a reaction mixture consisting of styrene, crotonyl peroxide and from 10% to by weight of methanol.

5. A process for the production of a synthetic resin which comprises heating styrene to a temperature of from 50 to C. in the presence of methanol and in the presence of cinnamyl peroxide.

6. A process for the production of a synthetic resin which comprises heating, to a temperature of from 50 to 100 C. a reaction mixture consisting of styrene, cinnamyl peroxide and from 10% to 60% by weight of methanol.

HANNS PETER STAUDINGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,683,404 ostromislensky Sept. 4, 1928 2,300,566 Hahn Nov. 3, 1942 2,310,961 Kropa Feb. 16, 1943 2,366,306 Alexander Jan. 2, 1945 2,381,561 Staudinger Aug. 7, 1945 FOREIGN PATENTS Number Country I Date 462,165 Great Britain Feb. 26, 1937 OTHER REFERENCES Brajnikoff: Plastics (London, July 1942), pp. 230-238, 

1. A PROCESS FOR THE PRODUCTION OF A SYNTHETIC RESIN WHICH COMPRISES POLYMERIZING A COMPOUND OF THE CLASS CONSISTING OF STYRENE AND ALPHAMETHYL STYRENE BY HEATING SAID COMPOUND TO A TEMPERATURE NOT IN EXCESS OF 150* C. IN THE PRESENCE OF A PEROXIDIC CATALYST CONTAINING THE RADICLE OF AN UNSATURATED ORGANIC ACID OF THE GROUP CONSISTING OF CROTONIC AND CINNAMIC ACIDS, AND IN THE PRESENCE OF A DILUENT CONSISTING OF AN ALIPHATIC ALCOHOL CONTAINING NOT MORE THAN FIVE CARBON ATOMS IN THE MOLECULE. 